Currently, the basic mechanisms of numerical control dual-end face spring grinders comprise an upper grinding wheel 01 and a lower grinding wheel 02, as shown in schematic views in FIGS. 1 and 2. The upper grinding wheel 01 can be moved up and down. A grinding disc 03, which is intended to contain springs 04, is provided in the space between the two end faces of the grinding wheels, and the grinding disc 03 is rotated around a fixed shaft. The spring grinder follows the basic working principle below: the grinding disc 03 is rotated around a fixed shaft, and as a result, the springs 04 on the grinding disc 03 are driven by the rotation of the grinding disc 03, and enter into the space between the two end faces of the grinding wheels from point a, and pass through point b to reach to point c, and get out of the space between the two end faces of the grinding wheels; then the springs 04 continue to be driven by the rotation of the grinding disc 03, and pass through point d from point c to reach to paint a once more; and the cycle is continued. During the whole process in which the springs 04 are driven by the grinding disc 03, the upper grinding wheel 01 is moved down slowly and the two end faces of the springs 04 in the space between the two end faces of the grinding wheels are ground. When the upper grinding wheel 01 is moved downwardly to the extent that the length of the ground spring 04 meets the requirement, the upper grinding wheel 01 is stopped moving and is then returned to the original point, and the grinding disc 03 is also rotated slowly. At this point, the operator opens the spring door, and then the ground springs 04 are removed out of the opening of the spring door one by one. After all the springs 04 are removed, the spring door is closed. Another complete spring 04 is placed onto the grinding disc 03 for the next grinding.
This working principle is suffered from the following disadvantages:
First, angle β is generally of 60 to 70 degrees, so that when the upper grinding wheel is moved downwardly, the time taken for the spring at point a on the grinding disc to pass through point b from point a to reach to point cis only about 17% of the time taken for the grinding disc to rotate in a full circle. Therefore, this results in three consequences: 1), Only about 17% of the complete spring is ground in the plane of the grinding wheels simultaneously, which leads to a low production efficiency. 2), The amount of grinding of each spring is only 17% of the amount of downward moving of the upper grinding wheel when the grinding disc is rotated in a full circle, while for the remaining 83% of the amount of moving, the spring is actually external to the grinding wheel and is not ground, which is unreasonable. The consequence of this is that the grinding at point a of the grinding wheel is very fast due to the sudden increase of the amount of grinding at point a, while the grinding at point b is slow and point c is almost not ground. Thus, the end face of the grinding wheel finally takes the shape of a truncated cone as shown in FIG. 3, which seriously affect the vertical precision of the spring grinding. 3), when the two grinding wheels are grinding, only the position coincident with the grinding disc is subjected to a force, and the amount of grinding at point a of the grinding wheels is very large, i.e., the primary grinding force is exerted on point a. The resultant axial force composed of the axial components of the grinding force is far away from the center line of the grinding wheel shaft. Therefore, the grinding wheel shaft and the grinding wheel disc have to bear a large bending moment, resulting in a large geometric deformation which is particularly obvious for the heavily ground spring, thus seriously affecting the precision of the spring grinding.
Second, because the grinding wheels are uneven when grinding, the end faces of the spring are actually not perpendicular to the plane of the spring axis, therefore, the spring cannot be brought to revolve in the whole process of grinding from point a to point c, which results in a low precision of the spring after being ground.
Finally, because there is no structure in the spring grinder for automatically regulating the interference of the bearing supporting the grinding wheel shaft currently, the precision and stability of the apparatus will degrade after being used for a period of time. To keep the precision and stability of the spring grinding, highly skilled workers are often required to manually regulate the interference of the bearing. In this way, not only such skilled workers are hard to find, but also the regulating to the interference of the bearing is troublesome.
In summary, currently, there is a need for innovation in both the working principle and the structure of the numerical control spring grinder whether seen from the point of apparatus structure and quality of the ground spring or from the point of grinding and production efficiency.
To this end, a further study is made by the present inventor to develop a method for grinding a spring with high quality and high efficiency from which the present application comes into being.